Make sure to think of all possible causes of a weak solenoid.
Had an issue with my Addams Family machine where the thing eject hole solenoid occasionally did not have the power to eject the ball. First I checked the solenoid alignment to the ball and ensured the plunger was not worn and moved freely in the sleeve. Still no good. Went a bit deeper and checked it was the correct coil type and checked the resistance with another of the same type. All good so I checked the voltage on the coil which was 70 volts on the 50 volt line which was fine.(the driver board caps etc. have recently been changed by a professional). Starting to scrap my head now??? I then though it must be a grounding problem. Checked the solenoid ground wire to the driver board which tested perfect. Dam plus some other words. Finally playing a game I noticed the coil was weaker when any flipper was held on. Great, must be a flipper issue. Checked the voltages at the flippercoils which all seemed fine and they all did what they are supposed to. Then by studding the driver board diagram I noticed the flippers and this coil are on the same feed from the transformer, connector J102 on the driver board. Unplugged it and plugged it back and BANG, problem solved!!!! The header pins have already been replaced so it looks like I need a new plug. By looking a bit deeper I probably saved de-soldering things or the purchase of a new coils etc. and end fix being just a couple dollars.
